I have a small ceph cluster (3 nodes, 5 osds each, journals all just partitions
on the spinner disks) and I have noticed that when I hit it with a bunch of
rados bench clients all doing writes of large (40M objects) with --no-cleanup,
the rados bench commands seem to finish OK but I often get health warnings like
HEALTH_WARN 4 requests are blocked > 32 sec;
2 osds have slow requests 3 ops are blocked > 32.768 sec on osd.9
1 ops are blocked > 32.768 sec on osd.10
2 osds have slow requests
After a couple of minutes, health goes to HEALTH_OK.
But if I go to the node containing osd.10 for example and do dump_historic_ops
I do get lots of around 20-sec durations but nothing over 32 sec.
The 20-sec or so ops are always "ack+ondisk+write+known_if_redirected"
with type_data = "commit sent: apply or cleanup"
and the following are typical event timings
initiated: 14:06:58.205937
reached_pg: 14:07:01.823288, gap= 3617.351
started: 14:07:01.823359, gap= 0.071
waiting for subops from 3: 14:07:01.855259, gap= 31.900
commit_queued_for_journal_write: 14:07:03.132697, gap= 1277.438
write_thread_in_journal_buffer: 14:07:03.143356, gap= 10.659
journaled_completion_queued: 14:07:04.175863, gap= 1032.507
op_commit: 14:07:04.585040, gap= 409.177
op_applied: 14:07:04.589751, gap= 4.711
sub_op_commit_rec from 3: 14:07:14.682925, gap= 10093.174
commit_sent: 14:07:14.683081, gap= 0.156
done: 14:07:14.683119, gap= 0.038
Should I expect to see a historic op with duration greater than 32 sec?
-- Tom Deneau
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